+ = It has plentiful research support. For example, Fox and Bailenson (2009) found that humans were more likely to imitate computer-generated ‘virtual humans’ who were similar to themselves, and Rushton and Campbell (1977) found that same-sex modelling significantly increased the number of female observers who agreed to, and then actually did, donate blood. These studies demonstrate support for different aspects of SLT, including modelling and vicarious reinforcement, adding credibility to the key principles of this theory.